In Vitro Biomechanical Comparison of a 4.5 mm Narrow Locking Compression Plate Construct Versus a 4.5 mm Limited Contact Dynamic Compression Plate Construct for Arthrodesis of the Equine Proximal Interphalangeal Joint

Benjamin J. Ahern, Brent L. Showalter, Dawn M. Elliott, Dean W. Richardson and Liberty M. Getman
April 2013
Veterinary Surgery



To compare the in vitro biomechanical properties of a 4.5 mm narrow locking compression plate (PIP-LCP) with 2 abaxially located transarticular screws and a 4.5 mm limited contact dynamic compression plate (LC-DCP) with 2 abaxially located transarticular screws using equine pasterns.

Study Design

Experimental. Paired in vitro biomechanical testing of 2 methods for stabilizing adult equine forelimb PIP joints.


Adult equine forelimbs (n = 8 pairs).


Each pair of PIP joints were randomly instrumented with either a PIP-LCP or LC-DCP plate axially and 2 parasagitally positioned 5.5 mm transarticular screws. The proximal aspect of the proximal phalanx (P1) and the distal aspect of the middle phalanx (P2) were embedded to allow for mounting on a mechanical testing machine. Each construct was tested in both cyclic and subsequently single cycle to failure in 4-point bending. The displacement required to maintain a target load of 1 kN over 3600 cycles at 1 Hz was recorded. Maximum bending moment at failure and construct stiffness was calculated from the single cycle to failure testing.


In cyclic testing, significantly more displacement occurred in the LC-DCP (0.46 ± 0.10 mm) than for the PIP-LCP (0.17 ± 0.11 mm) constructs (P = .016). During single cycle testing there was no significant difference in the bending moment between the LC-DCP (148.7 ± 19.4 N m) and the PIP-LCP (164.6 ± 17.6 N m) constructs (P = .553) and the stiffness of the LC-DCP (183.9 ± 26.9 N mm) was significantly lower than for the PIP-LCP (279.8 ± 15.9 N/mm) constructs (P = .011). All constructs failed by fracture of the bone associated with the transarticular screws and subsequently bending of the plates at the middle hole.


Use of the PIP-LCP resulted in a stiffer construct of the same strength as the LC-DCP in vitro using this 4-point bending model.